Fluid flow indicator



Dec' 16, 1941- E. J. MARTIN Er`AL FLUID FLOW INDICATOR Filed June 20, 1940 f s f1/wm IML occurring with relative deflection is measured. In the example illustrated, the distance between the portion it and the tube 6 is of the order oi! .091 o! an inch but is exaggerated in the drawing for the sake ci clarity.

It will be seen that the greatest change in capacity with a given relative deection of the parte and t will occur when the deflection is in the plane A--A of Fig.3, (i. e; in the direction in which the greatest change in the degree of separation of the greatest areas of the parts 8 and 9 is aected) Y The hollow reed or tube E, is provided with external diametrically opposite radial ns vi6 to provide a greater surface area for the velocity edect oi the fluid stream to act upon. and the device is assembled with these iins normal to the direction n n, or normal to the direction in which the greatest chance in capacity for e. given relative deflection of the parts takes place.

:if the direction oi the huid dow to be measured is known, the device is held in the huid stream with the iins i@ normal to the direction oi low. y Ii the direction of fluid ilow is not known, the device may be turned or oriented about its axis to that position in which the capacity changeis ereatest: the position of the slots it in the body i (which as illustrated are normal to the ijlns it) will then be an indication of the direction of flow.

The alternative fixed condenser element iii oi Figs. d and 6 is of haii circular section throughout the greaterpart oi its length; and is essentially the tubular fixed condenser element t' oi Fiss. 2, 3 and i with the unnecessary half portion it removed. v

it desired, the space between the fixed and deiecteble condenser elenients may be filled with any suitable dielectric material.

"'heuse of a closed hollow reed as the deilectable condenser element enclosing the tired condenser element, removes the possibility of moisture or foreign matter entering the indicator and "shorties" .the condenser elements.

VThe cylindrical construction of the deectable condenser element produces a very rigid member with a natural frequency which may be as high as decil cycles per second, that has little tendency to distort, while being sumciently sensitive to record deections by the fluid stream, because the capacity change taires place at the point of maxi-'- known manner. i

We claim:

l. In a iluid ilow indicating pick up device of 'the electrical capacity type in which the degree o! separation of a ilxed condenser element and a deilectable condenser element is varied by force dueto the rate of flow of the fluid stream to be measured, and changes the electrical capacity oi' the device in a. suitable electrical circuit, a deiiectable condenser element constituted i by a hollow reed the axis o! which extends from the body o! the device in. a. direction across the uid stream, and a fixed condenser element secured to one end of a central electrode insulated from but securely held inthe body oi the device, said xed condenser element projectins into the hollow reed, beingclosely spaced which the capacity change is greatest will be an index to the direction of fluid flow. and the actual capacity change in that position will be a measure of the rate of fluid ilow in that direction. Y

2. The combination according to claim l, in

which the hollow reed condenser elementis pro- SCDl vided with two radial nns disposed diametrically opposite each otherin e, plane normal to that direction oi' deflection oi the hollow reed in which the capacity change of the device for a given deflection is greatest.

3. The combination according to claim l., in which the fixed condenser element is of tubular form coaxial with the hollow reed, but is reduced in external diameter and thickness 'around half oi its circumference, whereby the reduced portion is spaced from the hollow reed by a distance many times greater than the remaining portion.

of the fixed condenser element and the hollow reed.

i. The combination according to claim i, in which the end of the hollow reed is closed.

5. The combination according to claim l, in which the fixed condenser element is Voi half circular cross-section concentric with the hollow reed.

6. The combination according to claim l', in which the hollow reed is integral with the body of the device.

7. An electrical condenserhaving condenser elements constituted respectively bye member which is a tubular extension of the body oi' the device, and a member securely held in the body of the device but insulated therefrom and projecting into the tubular extension from which it is suitably spaced, closely to one side thereofV and a relatively large ydistance from the opposite side thereof, said tubular extension being in the form of a hollow reed which is deflectable by a force transverse to its axis to vary the degree of separation hetweenthe members, and hence the capacity oi the condenser.

f EDWARD J. MARTIN CARL E. GRINSTEAD. ROBERT N. FRAWLEY. 

